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Scientific Methodology

The physics of molecular prediction. No shortcuts.

Every prediction in DrugSynq traces back to reproducible physics or ML models with documented validation datasets. We believe computational chemistry earns trust through transparent methodology, not marketing claims.

Conformer ensemble visualization showing multiple low-energy molecular conformations superimposed

Free Energy Perturbation

Thermodynamic rigor for SAR navigation.

Binding free energy differences (ΔΔG) are computed by running alchemical transformations in thermodynamic ensembles. Unlike docking scores, FEP directly accounts for explicit solvent, protein flexibility, and entropic contributions to binding.

DrugSynq uses Hamiltonian replica exchange (HREMD) to enhance conformational sampling across intermediate states, reducing hysteresis in perturbation legs and converging results in fewer nanoseconds of aggregate simulation time.

Explicit TIP4P-Ew solvent model; periodic boundary conditions
Soft-core potentials at λ=0 and λ=1 — no end-state singularities
BAR free-energy estimator with bootstrap error quantification
Results reported as ΔΔG ± σ (kcal/mol) — uncertainty visible by default
FEP Perturbation Legs
λ0
Fully coupled — reference state (Ligand A in protein)
λ¼
Intermediate — partial electrostatic decoupling, HREMD exchange
λ½
Intermediate — vdW decoupling + Coulomb off, soft-core active
λ1
Fully decoupled — end state (Ligand B in protein)

Force Field

OPLS4: parameterized for drug-like scaffolds.

OPLS4 introduced new torsional parameters for heterocycles and heteroatom environments common in drug-like molecules, addressing systematic errors in earlier force fields for aromatic amines, sulfonamides, and fluorinated compounds.

Heterocycle Coverage

Extended torsional coverage for pyridines, imidazoles, pyrimidines, and other N-heterocycles that appear in 78% of FDA-approved small molecule drugs.

Halogen Bonding

Explicit sigma-hole parameterization for chlorine, bromine, and iodine enables accurate modeling of halogen bond-mediated binding interactions in kinase and protease targets.

Solvation Accuracy

Hydration free energies for a test set of 450 drug fragments show mean absolute error of 0.45 kcal/mol vs. experimental values — critical for absolute binding free energy baselines.

ML-Enhanced Potentials

Physics backbone, ML correction layer.

For targets where crystallographic data is available but the binding site exhibits conformational flexibility not captured by rigid-ligand docking, DrugSynq applies machine-learned correction terms trained on high-quality QM reference data.

This hybrid approach (OPLS4 + ΔML correction) improves accuracy by approximately 0.2–0.4 kcal/mol RMSE on prospective test sets for kinase targets relative to OPLS4 alone, without adding interpretability concerns of pure ML models.

See Published Benchmarks
Accuracy Comparison (ΔΔG RMSE, kcal/mol)
Docking score only 2.1 kcal/mol
OPLS4 FEP 1.2 kcal/mol
DrugSynq (OPLS4 + ΔML) 0.9 kcal/mol
Benchmark set: 14 clinical targets, 312 congeneric pairs. See publications for protocol.

ADMET Architecture

Ensemble models from in vitro training sets.

Each ADMET model is an ensemble of gradient-boosted tree classifiers trained on standardized in vitro assay data from curated public databases supplemented with internal measurements from collaborator labs.

Training Data Curation

All training data passes structure standardization, duplicate removal, activity cliff detection, and assay condition normalization before model training. 247,000 curated data points across 12 assay endpoints.

Prospective Validation

Model performance is evaluated on held-out prospective datasets (compounds not in training timeline) to assess generalization rather than interpolation. Reported metrics are prospective AUROC and MCC.

Quarterly Model Updates

ADMET models are retrained quarterly as new in vitro data is incorporated. Subscribers receive notification when model versions change, with side-by-side accuracy metrics for continuity.

Published Accuracy

Metrics you can reproduce.

Performance numbers are published with data splits, code, and test set SMILES. If you can't reproduce it, we consider the benchmark unreported.

Endpoint Prospective AUROC Test MCC n (test)
hERG Inhibition 0.91 0.73 3,410
CYP3A4 Inhibition 0.88 0.68 5,820
Metabolic Stability (HLM) 0.85 0.61 2,190
Aqueous Solubility 0.87 0.66 4,750
Caco-2 Permeability 0.89 0.71 3,080
Metrics on held-out prospective test sets. Full protocol published in peer-reviewed literature — see Publications.

Published Research

Peer-reviewed evidence base.

J. Chem. Inf. Model. · 2025
Prospective Validation of Alchemical FEP Binding Affinity Predictions Across 14 Clinical Targets
Patel M, Krishnamurthy R, Chen S, Andersen MR.
JACS Au · 2024
Ensemble ADMET Prediction Models: Prospective Performance in Lead Optimization Campaigns
Chen S, Patel M, Krishnamurthy R.
View All Publications

Science you can build a drug program on.

Schedule a methodology review with our scientific team to evaluate fit for your target class and compound series.